Aerofoilboat

ABSTRACT

An aerofoilboat shaped with a concavity extending back from the bow, open at the front in the direction of forward motion and generally bounded at the sides and around the rear between the sides by the water surface, and with sufficient forward speed the aerofoilboat being raised and supported above the water surface primarily through an air cushion thereunder built up due to surface ground effect with forward motion of the aerofoilboat. It has a longitudinally shifting center of lift that moved toward the rear in a self adjusting trimming action as the boat moves higher and ground effects lift is lessened.

United States Patent Lippisch 51 May9, 1972 [54] AEROFOILBOAT [21] Appl.No.: 869,124

OTHER PUBLICATIONS Flight International Supplement, June 25, 1964, pps.80 and 81 Primary Examiner-Andrew l-l. Farrell Att0rney-Warren l-l.Kintzinger [5 7] ABSTRACT An aerofoilboat shaped with a concavityextending back from the bow, open at the front in the direction offorward motion and generally bounded at the sides and around the rearbetween the sides by the water surface, and with sufficient forwardspeed the aerofoilboat being raised and supported above the watersurface primarily through an air cushion thereunder built up due tosurface ground effect with forward motion of the aerofoilboat. It has alongitudinally shifting center of lift that moved toward the rear in aself adjusting trimming action as the boat moves higher and groundeffects lift is lessened.

7 Claims, 6 Drawing Figures PATENTEDMAY 9 I972 3,661 ,1 1

sum 1 [1F 3 IIIIIA III ALEXANDER M. LIPPISCH PATENTEDMAY 9 I9723.661.111

SHEET 2 OF 3 23 INVENTOR.

ALEXANDER M. LIPPISCH PATENTEDMAY 9 I972 SHEET 3 [1F 3 INVENTOR.

ALEXANDER M. LIPPISCH AEROFOILBOAT This invention relates in general toan aerofoilboat, and in particular, to an aerofoilboat with a concavitybeneath open from the bow and bounded below by the water surface andsupported thereabove primarily by ground effect with an air cushionbuilt up with normal velocity during operation.

Various air cushion vehicles are known that open toward the front andusing a ram air pressure area in the front, or bow, for building up anair cushion exerting a lifting force on the bottom of the vehicle. Someof these vehicles are also equipped with airfoil surfaces, some quitesimilar to airplane wings producing aerodynamic lift in relation toforward velocity. Consequently vehicles so equipped experience, duringforward operational movement, two different types of lifting forcescomplementing each other with one, being the lifting force of aircushion formed and maintained under the vehicle with continued forwardmotion, and, with the other, being aerodynamic lifting force developedwith the wings as determined by forward vehicle velocity. With some ofthese existing vehicles the wings and vehicle configuration is such thathigher velocities result in the aerodynamic force becoming the greaterforce and sufficient to at times, cause vehicle take-off and therebygreat reduction, if not complete reduction, of the surface, or ground,effect. Thus, special difficulties arise in attempts to attainstabilization of such vehicles in maintaining a precisely defineddistance above the water surface in a ground effect mode of operation.With some of the preexisting aerofoilboats propelled by air screws(propellers), and even with some other types of propulsion, there aredesign requirements and operational characteristics such as make theattainment of heights considerably higher than the extent of groundeffect the normal operational realm with greatly decreased air cushioneffect if any at all and the lifting force provided entirely, orsubstantially so, by vehicle wings.

It is therefore, a principal object of this invention to provide anaerofoilboat with stabilized operation maintained substantially entirelywithin ground effects throughout the full range of forward speeds abovelift-off and with the distance from the water surface maintainedsubstantially unchanged throughout this mode of operation independentlyof forward velocity above lift-off speed.

Another object in such an aerofoilboat is to attain such automaticallyregulated control of operational height in ground effect over the watersurface as to insure more efficient operation, and with water propellerpropulsion, insure substantially continuously maintained effectivevehicle propulsion propeller immersion in water.

Features of the invention useful in accomplishing these precedingobjects include, in an aerofoilboat, a design such as to produce onlylow lift at the forward portions high in ground effect, or effectivelyout of ground efiect, while the rear sectional portions of the boatincluding airfoils produce a much greater portion of the total liftexerted on the boat at such higher operational states. This results in avery effective automatic trimming action effectively maintainingoperation in ground efiect in a beneficially stabilized highly efficientmode of operation normally substantially never permitting free flight assuch to be attained. The vehicle is designed for use exclusively onwater or in ground effect above the water surface with forward vehiclevelocity attained through thrust obtained from water screw (propeller)rotation reaction in water, and with, in some embodiments,some if notall directional control obtained with water rudders. The automatictrimming control of the vehicle in ground effects prevents the boat fromtaking off so high, even at high speeds, as to result in such lifting ofwater propeller blading from water as to endanger control andpropulsion.

In order to keep the vehicle within the desired zone of surface effectthe effective center of total lift exerted on the boat must traveltoward the rear as the distance from the water surface is increasing.Ground effect can be utilized by the front parts of the vehicle onlythrough a relatively small distance range above the water surface witheffective ground effect lift obtained only in close proximity to thewater, while on the other hand, rearward airfoil components of thevehicle produce lift in relation to forward speed. When, at high speeds,the boat rises above the water surface more than close clearance inground effect, pure ram pressure on the boat bottom decreases rapidlywhile the lifting force produced by wings and, or tail airfoil is notsubstantially reduced. This thereby accomplishes the desired rearwardtrimming action shift of the effective center of lift toward the rearwith boat attitude being corrected to maintain the desired effect zoneof operation. This inherent design feature with automatic ground effectaltitude maintained trimming insures efficient continued water immersionof propeller and rudder.

There are other considerations including location of the power plant andpropeller, since at high velocity the wake of the water screw, orscrews, produces a high rising powerful spray. Further since enginesrepresent a major portion of the total weight of such vehicles they mustbe installed close to the center of gravity. This is advantageously,most favorably, accomplished through locating power plants in the middlesection of the boat close to the center of gravity. Tail booms areprovided extending rearwardly from the central body of the vehicles tomount a horizontal stabilizer plane at extreme rear. These stabilizerelevator surfaces are mounted sufficiently high to be primarily out ofground effect through the full range of vehicle operation, and inaddition, to providing a vehicle aerodynamic stabilizing effect theyderive lift primarily as an aerodynamic airfoil with forward motionthrough the air.

With some vehicle embodiments airfoils are provided, concave toward thewater surface and convex on the top, attached to opposite sides of theboat toward the rear thereof. Such wings are particularly useful forrelatively slower aerofoilboat embodiments, since they advantageouslyincrease the lift of the boat as a whole or, stated another way, attainthe required lift for desired operation at lower speeds. At the sametime with the rearward location of these added side wings a higherincreasing portion of the total lift is provided toward the stern thanat the bow with increasing distance above the water thereby attainingthe automatic trim return of the boat to desired ground effect zonaloperation, relative to the water surface. With some higher speedvehicles the desired stabilizing trimming action is attained in anaerofoilboat without wings other than an elevator stabilizer plane.

Referring to power plant location the most effective is on the centralaxis of the boat, and in the case of multiple power plants in symnetryclose to the central axis. Further, with some embodiments tail boomsrise as they extend to the rear to minimize the effect of water sprayimpingement thereon and to prevent, or minimize, any obstruction toforward propulsion that may arise therefrom.

In the embodiments having rearwardly located wings the wings havelateral and rear edges situated at about the same level as, if notcommon to, a plane bounding the fuselage (or boat body) at the bottom.With such design ram air pressure is built up not only in the concavityopen from the bow of the boat hull or body, but, additionally, under thelaterally at tached wing surfaces extending towards the rear. Thus,these additional wings serve a double purpose: first, in the build up ofair cushions thereunder through ground effect and, secondly, to produceaerodynamic lift independently of surface ram air and ground effect, asin the case with airplane wings. Since the side wing surfaces extenddownward to their lateral and rear bounding edges, they form rampressure areas or pockets thereunder over the water surface, leading toram air creation of air cushions as vehicle forward velocity is initatedand built up much the same as with concavity of the body extending fromthe bow thereof. When the aerofoilboat rises from the water surface rarneffect derived pressure air begins escaping toward the sides and theback with some lessening of lifting force based on ground effect andsome increase in lift derived from increased suction on the top ofaerodynamic wing type surfaces along with increased pressure on thebottom surfaces. With lateral lifting surfaces attached to the rear partof a boat body and lifting force therefrom becoming more predominatetoward the stern of the vehicle results in return of the boat bow backdown to a level low enough above the water surface for ram pressure andground effect build up in the concavity of the bow to automaticallymaintain operating trim of the vehicle.

Specific embodiments representing what are presently regarded as thebest modes of carrying out the invention are illustrated in theaccompanying drawings.

In the drawings:

FIG. 1 represents a perspective view of an aerofoilboat equipped withrearwardly located side wings;

FIG. 2, a longitudinal section of the aerofoilboat of FIG. 1;

FIG. 3, a top plan view of an alternate embodiment of an aerofoilboatfrom the embodiment of FIG. 1 also employing rearwardly located sidewings;

FIG. 4, a front view of the aerofoilboat of FIG. 3;

FIG. 5, a top plan view of another alternate embodiment of anaerofoilboat not employing side wings as with the embodiments ofFIGS. 1and 3; and

FIG. 6, a longitudinal section of the aerofoilboat of FIG. 5.

Referring to the drawings:

The aerofoilboat body of FIGS. 1 and 2 is designed with an inclinedbottom surface forming a cavity 1 1 opening toward the front at the bodybow. Twin mirror image tail booms 12 attached to body 10 extendtherefrom to the rear to carry rearwardly located tail fins 13, and areequipped with side wings 14 extending outwardly from the rear sides ofthe body and the booms 12. The tail fins l3 advantageously mount, ontheir upper ends, an interconnecting stabilizer 15 extendedtherebetween. Between the transverse spacing of the two tail booms 12and longitudinally between the vehicle body 10 and the stabilizer 15there is free rearward open area generally accommodating high risingwater spray generated by water propellers of such vehicles. The body 10extends to this open area with a stem end mounting of engine 16 locatedbehind the center of the body 10 and behind a passenger cabin enclosure17 equipped with seats 20. With this embodiment a combined rudder l8 andpropeller 19 drive assembly is used that projects downwardlysufficiently far to insure efficient operational immersion of thepropeller 19 and rudder 18 through substantially all normallyencountered conditions of operation. Please not that water propellerpropulsion may be replaced by other types of propulsion such as, forexample, water jet propulsion. The side wing airfoils 14 are attachedmainly to the outer sides of the tail booms 12 extending towards therear of the aerofoilboat. These wing airfoils rise slightly from therear towards the front, and front to rear vertical sections thereofcorrespond to like sections through wings of an airplane. The rear edgesof these wings 14 skim over the water surface thereby facilitating viathe airfoils 14, advantageously fitted with outer end floats 21, theformation of ram pressure areas thereunder at normal cruising speedwhile the boat is flying in ground effect.

With the aerofoilboat embodiment of FIGS. 3 and 4 a boat body 22 roughlytriangular in plan view as viewed from above in FIG. 3 has a bottomconcave surface 23 extending from edge to edge at the body front betweenforwardly extended floats thereof. This bottom concave surface 23 has,generally, the shape of a cone surface section extending from a largeend at the front bow end to, substantially, the rear tip end of the bodytriangular shape. Airfoil wings 24 and 25 are attached to opposite sidetriangle edges of body 22. A propulsion unit 26 is installed at the reartip end of the body. Further, vertical tail planes 27 and 28 are mountedon the top rear of airfoil wings 24 and 25, respectively, and areinterconnected at their upper ends by stabilizer plane 29 mountedthereon, With some similarity to the embodiment of FIG. 1 the airfoilwings 24 and 25 extend outward and down to outer end floats, anddownward to combined outer and trailing edges forming ram air pressurecavities above the water surface.

Referring now to the aerofoilboat embodiment of FIGS. 5 and 6 a boat ispresented that is designed for relatively high speed operation withoutrearward side mounted wings such as used with the embodiments of FIGS. 1and 3. This high speed embodiment has a relatively wide body 30 with aram air pressure cavity 31 open from the bow and extended transverselybetween outer edge forwardly extending floats.The bottom concave surfaceof cavity 31 forming the vehicle rarn air pressure area tapers down tothe trailing bottom edge at the rear of body 30. Tail booms 32 and 33,generally in longitudinal plan view alignment with respective oppositebody edge forwardly extended floats, rising generally toward the rearare each terminated in a vertical rudder plane. These two rudder planesmount at their tops a relatively highly positioned stabilizer plane 34spanning the horizontal distance between the two rudder planes. Thisstabilizer plane 34 develops a sufficient aerodynamic lift increase atthe stern of the boat with speed increase to automatically counteractincreased pressure trying to lift the boat bow ocurring with increasedvelocity in automatic trimming efficiently to desired ground effectwater surface spacing with no other lifting surfaces required.

Whereas this invention is herein illustrated and described with respectto specific embodiments hereof, it should be realized that variouschanges may be made without departing from the essential contributionsto the art made by the teachings hereof.

I claim:

1. An aerofoilboat, supported above the water by utilizing an aircushion forming due to the ground effect phenomenon: having, a concavityopen from the bow in the direction of forward motion of theaerofoilboat, and with the concavity, bounded below, generally, by thewater surface; a propulsion unit with at least one propeller positionedfor turning in water during operation; with aerofoilboat forward sectiondesigned to produce relatively low lift in flight outside of groundeffect and provide a ground effect center of lift forward from anaerodynamic component center of lift; with an aerodynamic lift airfoilsection of the airfoilboat located toward the rear, producing anincreasing portion of the total aerofoilboat lift as the boat movesprogressively higher in the ground effect zone of operation, andproducing higher lift in flight outside of ground effect; and with saidpropulsion unit a powerplant positioned in a center cut-out area of theboat close to the center of gravity in the boats body.

2. The aerofoiboat of claim 1, including airfoils, with convex topsurfaces and concave bottom surfaces, attached to the sides of the boat.

3. The aerofoil boat of claim 2, in a high speed configurationincluding, tail booms extended to the rear; and a stabilizer planeattached to the tail booms.

4. An aerofoilboat, supported above the water by utilizing an aircushion forming due to the ground effect phenomenon; having, a concavityopen from the bow in the direction of forward motion of theaerofoilboat, and with the concavity, bounded below, generally, by thewater surface; a propulsion unit with at least one propeller positionedfor turning in water during operation; with aerofoilboat forward sectiondesigned to produce relatively low lift in flight outside of groundeffect and provide a ground effect center of lift forward from anaerodynamic component center of lift; with an aerodynamic lift airfoilsection of the aerofoilboat located toward the rear, producing anincreasing portion of the total aerofoilboat lift as the boat movesprogressively higher in the ground effect zone of operation, andproducing higher lift in flight outside of ground effect; includingairfoils with convex top surfaces and concave bottom surfaces, attachedto the sides of the boat; and with said airfoils with lateral and rearedges generally at substantially the level of a common plane with thebottom of the body of the aerofoilboat.

5. The aerofoilboat of claim 4, in a high speed congifuration including,tail booms extended to the rear; and a stabilizer plane attached to thetail booms.

6. The aerofoilboat of claim 1, in a high speed configuration including,tail booms extended to the rear; and a stabilizer plane attached to thetail booms.

aerodynamic component center of lift; with an aerodynamic lift airfoilsection of the aerofoilboat located toward the rear, producing anincreasing portion of the total aerofoilboat lift as the boat movesprogressively higher in the ground effect zone of operation, andproducing higher lift in flight outside of ground effect; in a highspeed configuration including, tail booms extended to the rear; and astabilizer plane attached to the tail booms.

1? k l l

1. An aerofoilboat, supported above the water by utilizing an air cushion forming due to the ground effect phenomenon: having, a concavity open from the bow in the direction of forward motion of the aerofoilboat, and with the concavity, bounded below, generally, by the water surface; a propulsion unit with at least one propeller positioned for turning in water during operation; with aerofoilboat forward section designed to produce relatively low lift in flight outside of ground effect and provide a ground effect center of lift forward from an aerodynamic component center of lift; with an aerodynamic lift airFoil section of the airfoilboat located toward the rear, producing an increasing portion of the total aerofoilboat lift as the boat moves progressively higher in the ground effect zone of operation, and producing higher lift in flight outside of ground effect; and with said propulsion unit a powerplant positioned in a center cut-out area of the boat close to the center of gravity in the boat''s body.
 2. The aerofoiboat of claim 1, including airfoils, with convex top surfaces and concave bottom surfaces, attached to the sides of the boat.
 3. The aerofoil boat of claim 2, in a high speed configuration including, tail booms extended to the rear; and a stabilizer plane attached to the tail booms.
 4. An aerofoilboat, supported above the water by utilizing an air cushion forming due to the ground effect phenomenon; having, a concavity open from the bow in the direction of forward motion of the aerofoilboat, and with the concavity, bounded below, generally, by the water surface; a propulsion unit with at least one propeller positioned for turning in water during operation; with aerofoilboat forward section designed to produce relatively low lift in flight outside of ground effect and provide a ground effect center of lift forward from an aerodynamic component center of lift; with an aerodynamic lift airfoil section of the aerofoilboat located toward the rear, producing an increasing portion of the total aerofoilboat lift as the boat moves progressively higher in the ground effect zone of operation, and producing higher lift in flight outside of ground effect; including airfoils with convex top surfaces and concave bottom surfaces, attached to the sides of the boat; and with said airfoils with lateral and rear edges generally at substantially the level of a common plane with the bottom of the body of the aerofoilboat.
 5. The aerofoilboat of claim 4, in a high speed congifuration including, tail booms extended to the rear; and a stabilizer plane attached to the tail booms.
 6. The aerofoilboat of claim 1, in a high speed configuration including, tail booms extended to the rear; and a stabilizer plane attached to the tail booms.
 7. An aerofoilboat, supported above the water by utilizing an air cushion forming due to the ground effect phenomenon: having, a concavity open from the bow in the direction of forward motion of the aerofoilboat, and with the concavity, bounded below, generally, by the water surface; a propulsion unit with at least one propeller positioned for turning in water during operation; with aerofoilboat forward section designed to produce relatively low lift in flight outside of ground effect and provide a ground effect center of lift forward from an aerodynamic component center of lift; with an aerodynamic lift airfoil section of the aerofoilboat located toward the rear, producing an increasing portion of the total aerofoilboat lift as the boat moves progressively higher in the ground effect zone of operation, and producing higher lift in flight outside of ground effect; in a high speed configuration including, tail booms extended to the rear; and a stabilizer plane attached to the tail booms. 